Controllers are known to utilize pressurized fluid to actuate a unit, such as a motor valve, to control a primary variable condition, such as a fluid level confined within a storage vessel, by maintaining the fluid level within the storage vessel within predetermined limits. Changes in the fluid level within the storage vessel are used by the controller to selectively apply the pressurized fluid to the unit, such as a motor valve controlling the flow of fluid through an inlet line attached to the storage vessel. Other applications and uses for pressurized fluid controllers are well known in the art.
One type of pressurized fluid control device is epitomized by the pressure control device disclosed within U.S. Pat. No. 3,120,241 issued to Asbury S. Parks on Feb. 4, 1964 (Parks '241). Although Parks '241 discloses a functional controller, controllers utilizing the technology disclosed by Parks '241 inherently present a number of drawbacks including: the encountering of significant downtime when defective diaphragms need replacement; and the need to reconfigure the pilot pressure control device, which interacts with the fluid level detection mechanism to control the fluid level within the vessel, and to change to operating mode of the controller from a direct mode to an indirect mode.
Accordingly, as market pressures continue to demand liquid level controllers that provide lower cost, greater reliability, and improved ease of use, challenges remain and a need persists for improvements in methods and apparatuses for use in fluid level monitoring and control devices.